Congenital Chylous Ascites in a Neonate with Isolated Aqueductal Stenosis: A Case Report and Literature Review.

Background and Clinical Significance: Ventriculoperitoneal (VP) shunting remains the standard definitive treatment for progressive neonatal obstructive hydrocephalus. Congenital chylous ascites is an uncommon neonatal condition, most often related to developmental lymphatic abnormalities. The concurrence of hydrocephalus requiring VP diversion with congenital chylous ascites is exceptionally rare and may first become apparent during abdominal access for shunt placement. Awareness of this possibility is clinically important because milky peritoneal fluid at shunt surgery can mimic gastrointestinal injury, and persistent postoperative abdominal fluid collections may be misattributed to shunt-related complications. Case Presentation: A late-preterm female infant (36 weeks' gestation; birth weight 2.3 kg) presented with congenital hydrocephalus. Cranial ultrasonography was consistent with isolated aqueductal stenosis. Preoperative abdominal ultrasonography demonstrated mild ascites. On 27 May 2025, a VP shunt was placed for obstructive hydrocephalus. Upon entering the peritoneal cavity, milky-white fluid was encountered, prompting concern for bowel injury; however, careful exploration showed no gastrointestinal perforation. Ascitic fluid analysis revealed markedly elevated triglycerides (2300 mg/dL), confirming chylous ascites. The VP shunt was completed without an intraoperative complication. During follow-up, the infant showed appropriate growth (weight 3.0 kg; length 50 cm), while ascites persisted, and she was referred for multidisciplinary evaluation and management. Conclusions: This case highlights an exceptionally rare association of congenital chylous ascites with isolated aqueductal stenosis, identified incidentally during VP shunt insertion. Prompt intraoperative recognition, biochemical confirmation, and coordinated follow-up are essential to distinguish congenital chylous ascites from shunt-related abdominal fluid collections and to guide appropriate multidisciplinary care.